A so-called ink jet recording method of performing recording by splashing liquid drops of a recording liquid containing a water-soluble dye such as a direct dye and an acidic dye, through fine jetting orifices are being used in practice.
The recording liquid is required to be fixed rapidly on a recording sheet commonly used for general office works, such as PPC (plain paper copier) for electrophotographic sheet and fanfold paper (continuous form for computers or the like), to provide a printed matter having good printing appearance grade, namely, a clearly outlined printed letter free of blurring, and to have excellent stability during storage as a recording liquid. Accordingly, the solvent which can be used is extremely limited.
On the other hand, the dye for use in the recording liquid is required to have a sufficiently high solubility in the above-described limited solvents, to be stable during a long-term storage as a recording liquid, to provide a printed image having a high density and to have excellent water resistance and light fastness. These requirements are, however, difficult to satisfy all at the same time.
To overcome the difficulties, various proposals have been presented (for example, see JP-A-61-101574 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-A-61-101576, JP-A-61-195176, JP-A-61-62562, JP-A-61-247771, JP-A-62-156168, JP-A-62-246974, JP-A-63-63765, JP-A-63-295685, JP-A-1-123866, JP-A-1-240584, JP-A-2-16171, JP-A-3-122171, JP-A-3-203970, JP-A-4-153272). However, the requirements on the market have not yet been fully satisfied.
JP-A-4-279671 and PCT International Publication WO 94/16021 teach that a dye having a structure such that two molecules of a specific monoazo-base dye having a triazinyl group are connected through a divalent organic bond group can be used for the ink jet recording.
However, in the former publication, the divalent organic bond group as a linking group does not play an important role and only linking groups such as (substituted) phenylenediamine are described as the example thereof. These linking groups have a planar structure and when a dye having such a linking group is used, the recorded image is inferior in the coloring property and a sufficiently high color density is not achieved.
Further, the group has a conjugated system and when this group is present, a deep color tone is presented and a deeply blue-tinted color results. Furthermore, the group (the group represented by Z and corresponding to the group represented by x.sub.1 or X.sub.2 in the present invention) bonded to the triazinyl group is preferably a group of which N atom is directly bonded to the triazinyl group, such as NHC.sub.2 H.sub.4 OH and morpholino group, and in the Examples, only dyes having such a structure are used. This type of dye also has a tendency to decrease in the saturation of the image color.
In the latter publication, the divalent organic bond group as a linking group is a (substituted) phenylenediamine group or a substituted piperazine group. Of these divalent organic bond groups, the (substituted) phenylenediamine group is not preferred because of the reasons described above. Further, when substituted piperazine is used as the divalent organic bond group, the dye is deficient in the light fastness and the water resistance as specifically verified later in Comparative Example 2.
JP-A-8-218021 teaches that a dye having a structure such that two molecules of a specific monoazo-base dye having a triazinyl group are connected through a divalent organic bond group can be used for the ink jet recording. However, the structure of the linking group differs from that of the present invention and the dye is low in the reliability and fails to provide the light fastness and color tone of a satisfactory level.